Elucidating the Roles of Amorphous Alumina Overcoat in Palladium-Catalyzed Selective Hydrogenation

[Image: see text] Amorphous alumina overcoats generated by atomic layer deposition (ALD) have been shown to improve the selectivity and durability of supported metal catalysts in many reactions. Several mechanisms have been proposed to explain the enhanced catalytic performance, but the accessibilities of reactants through the amorphous overcoats remain elusive, which is crucial for understanding reaction mechanisms. Here, we show that an AlO(x) ALD overcoat is able to improve the alkene product selectivity of a supported Pd catalyst in acetylene (C(2)H(2)) hydrogenation. We further demonstrate that the AlO(x) ALD overcoat blocks the access of C(2)H(2) (kinetic diameter of 0.33 nm), O(2) (0.35 nm), and CO (0.38 nm) but allows H(2) (0.29 nm) to access Pd surfaces. A H–D exchange experiment suggests that H(2) might dissociate heterolytically at the Pd–AlO(x) interface. These findings are in favor of a hydrogen spillover mechanism

Construction of Inverse Metal–Zeolite Interfaces via Area-Selective Atomic Layer Deposition

[Image: see text] The spatial confinement at metal–zeolite interfaces offers a powerful knob to steer the selectivity of chemical reactions on metal catalysts. However, encapsulating metal catalysts into small-pore zeolites remains a challenging task. Here, we demonstrate an inverse design of metal–zeolite interfaces, “metal-on-zeolite,” constructed by area-selective atomic layer deposition. This inverse design bypasses the intrinsic synthetic issues associated with metal encapsulation, offering a potential solution for the fabrication of task-specific metal–zeolite interfaces for desired catalytic applications. Infrared spectroscopy and several probe reactions confirmed the spatial confinement effects at the inverse metal–zeolite interfaces